System of electric ship propulsion



F. A. HAIGH SYSTEM OF ELECTRIC SHIP PROPULSION Feb. 1925- 1,527,643

Filed July 17. 1923 A Ra Irv/enter:

Frederick A. Haigh, b flq/M 4 His Attor-h 0y.

Patented Feb; 24, 1925. r UNITED STATES PATENT ()FFICE.

' a subject of the driven by independent internal ,of an engine,

.vention' consists in exciting number of generators an FREDERICK A. HAIGH, 0F RUGBY, ENGLAND,

assroivoa r0 GENERAL ELECTRIC oom- PANY, a conromrrolv or NEW YORK. SYSTEM or ELECTRIC sm PROPULSION.

ama aim m 17,

i To all whom it may concern:

'- Be it known that I, Fnnnnnroir A. HAIGH,

British Empire, residing at Ru by, in the county of Warwick, England, have invented certain new and'useful Improvements in Systems of Electric Ship Propulsion, of WhlCh the following is a specification.

y invention relates to systems of electric ship propulsion and more articularly to systems in which a number 0 generators combustion engines supply current to a motor on the propeller shaft. In such systems it is necessary to provide means for preventing the reversal of rotation of one-of the generators should the engine driving it fail for any reason to maintain the necessary driv- 1ng torque, as for example by the failure of the fuel supply or the sticking of the valves. The object of the present invention is -to provide means ing the reversal of the direction of rotation of the generator in the event of the failure and at the same time automatically decreasing the field of the propeller drivin motor so as to reduce its field strength an thereby compensate for the drop in'voltage at its terminals. The inthe fields of each enerator from a sel or separately elicited exciter mounted on, coupled to or driven-from the generator shaft, so that an decrease of speed of the generator itself will automatically weaken. its fiel The invention further consists in dividing the field of the propeller motor'into a number of sections corres onding to the excitin each section of the propeller motor fiel from the exciter of one of the generators or from the generatorarmature voltage, so that in the event of one of the generators failin a corresponding section of the motor fiel is automatically weakened or out out. and the total field strength of the motor thereby reduced. v

In carrying this invention into. effect, I may provide four generators each driveny a separate internal combustion engine, these generators being connected in series and supplying current to a motor mounted on the propeller shaft. In the event of failure of one of the engines, the tendency would be for the remaimng three generstrength and for automatically prevent-' the motor speed and,

- however, the volta 1923. Serial N0. 852,198.

first ofall tend to stall or bring to rest the defective (generator set and will then tend to reverse its directionof rotation and drive 1 it in the opposite direction, thereby driving the engine in the wrong direction. This might cause serious da age to the installatron and to prevent it i provide an exciting machine either mounted on or driven by the shaft of each generator instead of as is the usual practice, exciting all the generators from a single exciter.

In such an arrangement inthe event of a failure of one of the engines, the field consequently the torque of. the corresponding generator would fall rapidly with the speed and there would be no torque available to reverse the rotation of the set.

The reduction in the voltage available for the motor would result in a reduction of since the power absorbed by a ropeller falls more rapidly than the speed, the current in the system would be reduced and the remaining gines would be unable to deliver their full power to the propeller. By dividing the motor field into sections each dependent on the excitation of one of the generators, the total resultant motor field would be weakened as the voltage availablefor the motor armature was reduced, and the motor speed could thus be maintained at approximately the value required to utilize the ower available. In such an arrangement in the event of failure of one of the engines t-he exciter of the generator driven thereby a'utomatically fails'to supply current to the field of the generator, so that it is not possible for this machine to reverse and run as a motor driving the prime mover.

With this generator cut out of circuit,

e supplied to the ropeller motor woulc drop considerably and thereb reduce the speed of the propeller. In or er to prevent this, I' divide the field of the motor into four sections, each section being supplied with current from the exoiter of one'of the generators. On failure of one of the rime movers the exciter driven thereby fiails to supply current to the section of the field usually supplied by it. This automatically weakens the total field of the motor and tends to raise its current speed thereby compensat' for the drop in voltage caused by one o the generators having been put out of action.

My-in'vention will be better understood upon reference to the following description taken in connection with the accompanying.

drawings and its scope will be pointed out by the appended claims.

to the drawing, Fig. 1-

respondin generator and to a section 6 of I the propel er motor field winding. Switches 7 may be provided, for short-circuiting a motor 2 when it is not in use. The field circuit of each motor 2 is shown as provided with an adjustable rheostat 8. In order to permit operation ofthe motor 4 in both directions by Ward Leonard'control each rheostat 8 may be replaced by a reversing rheostat of the type shown in Fig. 2.

What I claim as new and desire'to secure by Letters Patent of the United States, is,-

1. A system of electric ship propulsion wherein a plurality of direct current generators driven by diflz'erent prime movers and supplied with current from separate exciting machines are arranged to supply current to a propeller motor provided wit a shunt field windin characterized by-"the fact that said shunt eld winding is divided into sections supplied with current from different exciting machines whereby the field strength of said motor may be controlled-in response tothe number of exciting machines in operation.

2..A system of electric'ship'propulsion comprising a plurality ofdirect. current generators, an exciting machine mounted on the shaft of each generator, and a propeller motor arranged to be supplied with current from said generators, said motor being provided with a shunt field winding divided into sections conductively related to different exciting machines,

3. A system of electric erators, a prime moverfor driving each a generator, an exciting machine mounted on the shaft of each generator and arranged to supply current to the field winding of one of said generators,'and a propeller motor connected in series with said generators and 4. A ship propulsion system wherein a plurality of series-connected generators each havingv an exciting machine mounted on its shaft are arranged to supply current to a propeller motorand wherein a difierent prime mover is provided for driving each of said generators, characterized by the fact that said generators are supplied with'excitation from the exciting machines mounted on their respective shafts, whereby each generator is enabled to operate at reduced torque upon a decrease in the'speed and torque of its, prime mover.

5'. A'ship propulsion system j wherein a plurality o series-connected generators are arranged to supply current to a propeller motor andwherein'a different prime mover is provided for driving each of said genera tors, comprisin a difierent exciting maship propulsion comprlsing a plurality ofdirect current genchine for supp ying"excitationto each of 1 said generators, each exciting machine being arranged to rotate at a speed proportional to the speed of the generator to which it supplies exciting current.

In witness whereof, my hand this twenty-sixth day of June, 1923. a a

Witnessesi .J. A. Poem, Dono'rin Wmrs.

I have hereunto set FREDERICK A. HAIGH. 

